Gear Nomenclature, Definition of Terms with Symbols

ANSI/AGMA 1012-H23

ANSI/AGMA 1012-H23


This standard lists terms and their definitions with symbols for gear nomenclature.


In 1926 the AGMA adopted a recommended practice for gearing nomenclature, terms and definitions. It included some symbols and abbreviations.

A complete revision of terms and definitions by the AGMA Nomenclature Committee was issued as AGMA 112.02 in October 1948. This later became AGMA 112.03, and American Standard B6.10-1954, with ASME as a co-sponsor.

A separate project dealing with Letter Symbols for Gear Engineering appeared in 1943 as AGMA 111.01, later becoming AGMA 111.03 and American Standard B6.5-1954.

Abbreviations for Gearing was another separate project released as AGMA 116.01 in 1955. Most of these abbreviations were already listed in American Standard Z32.13-1950 Abbreviations for Use on Drawings, and it was, therefore, unnecessary to process gearing abbreviations as a separate American Standard. The number of abbreviations used in gearing has intentionally been kept very small to permit memorizing without the need to refer to the standard.

AGMA Standard 112.04, Gear Nomenclature (Geometry) Terms, Definitions, Symbols and Abbreviations, was a complete revision and integration of the three standards previously mentioned. Because of the widespread acceptance of the previous standards, changes were kept to a minimum. The standard in this form was approved by the AGMA Membership on April 25, 1965.

AGMA 112.05 included several revisions to keep it abreast of the then-current gearing techniques. It was approved by Standards Committee B6, Gears, the Co-Secretariats and the American National Standards Institute on February 3, 1976 and designated ANSI B6.14-1976.

ANSI/AGMA 1012-F90 was a revision of 112.05. This revision incorporated the terms from AGMA Standard 116.01 (October 1972), Glossary of Terms Used in Gearing, and terms from ANSI/AGMA 2000-A88, Gear Classification and Inspection Handbook, Tolerances and Measuring Methods for Unassembled Spur and Helical Gears (Including Metric Equivalents). In addition, terms which started to be commonly used in gear load rating were introduced in the annex.

ANSI/AGMA 1012-G05 is a revision that updates the style of presentation, reordered the sequence of some terms, added definitions for right and left flank, and modified Annexes B and C.

The first draft of ANSI/AGMA 1012-G05 was made in June 2002. It was approved by the AGMA membership in July 2005. It was approved as an American National Standard on September 29, 2005.

ANSI/AGMA 1012-H23 replaces ANSI/AGMA 1012-G05. The changes in this edition include extensive updates of text and figures, and the annexes have been eliminated.

The first draft of ANSI/AGMA 1012-H23 was made in July 2016. It was approved by the AGMA membership on October 28, 2022. It was approved as an American National Standard in March 2023.



This standard defines terms relating to the rating and tooth geometry for cylindrical, bevel, hypoid, worms, and face gears. The definitions use illustrations and equations when necessary.

NOTE: While some common trade names are included, it is beyond the scope of this standard to define all gear trade names.


The following documents contain provisions which, through reference in this text, constitute provisions of the standard. At the time of publication, the editions were valid. All publications are subject to revision, and the users of this standard are encouraged to investigate the possibility of applying the most recent editions of the publications listed.

ISO 701, International gear notation – Symbols for geometrical data

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